INTERNATIONAL STANDARD

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1 INTERNATIONAL STANDARD ISO 9112 Second edition Truck and bus tyres Methods of measuring tyre rolling circumference Loaded new tyres Pneumatiques pour véhicules utilitaires et autobus Méthodes de mesure de la circonférence de roulement Pneumatiques neufs en charge Reference number ISO 9112:2008(E) ISO 2008

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3 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 9112 was prepared by Technical Committee ISO/TC 31, Tyres, rims and valves, Subcommittee SC 4, Truck and bus tyres and rims. This second edition cancels and replaces the first edition (ISO 9112:1991), which has been technically revised. ISO 2008 All rights reserved iii

4 Introduction The distance covered by a vehicle in a straight line in one wheel revolution is information that is increasingly used by the electronic systems in vehicles. One reason is that it makes it possible to indicate the instantaneous vehicle speed to the driver. Its evaluation uses the rolling circumference of the tyre in normal usage conditions: tyre deflected by the carried load and inflated to an adapted pressure level. A standardized measuring method is necessary because some parameters, such as tyre load and pressure, can cause the rolling circumference to change. This International Standard contributes to tyres being interchangeable for a given vehicle. Its application by tyre manufacturers allows confidence to be maintained in the information provided to the driver, especially concerning speed and distance travelled. iv ISO 2008 All rights reserved

5 INTERNATIONAL STANDARD ISO 9112:2008(E) Truck and bus tyres Methods of measuring tyre rolling circumference Loaded new tyres 1 Scope This International Standard specifies two methods for measuring the rolling circumference and the number of revolutions per unit distance (kilometre) of new commercial vehicle tyres, under loaded conditions, for use on trucks and buses. The first method is a drum method consisting of loading a test tyre mounted on a free axle against a driven road wheel (or drum) of specified diameter. The second method involves a vehicle whose drive axle is equipped with the test tyres driven on a straight, paved road. The values thus obtained are not intended for use as levels of performance or quality. This International Standard applies to all truck and bus tyres. NOTE This International Standard applies not only to large truck and bus tyres, but also to small truck and bus tyres, which are called light truck tyres in some countries. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO , Truck and bus tyres and rims (metric series) Part 1: Tyres 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 revolutions per unit distance number of tyre revolutions (and portions thereof) that occur when the (axle) centre of the tyre is moved exactly the unit distance of 1km, under the conditions specified in this International Standard 3.2 rolling circumference of tyre distance that the (axle) centre of the tyre moves in one revolution of the tyre, under the conditions specified in this International Standard 3.3 reference speed speed at which the test is intended to be performed and which is related to the delivered value of the rolling circumference ISO 2008 All rights reserved 1